Many devices are marketed today for measuring and/or analyzing the refractive properties of transmissive devices. A specific area is well known to be in optical systems including ophthalmic lenses. Various issued patents are directed to such devices such as prior issued U.S. Pat. No. 3,832,066--Cornsweet, issued Aug. 27, 1974 and U.S. Pat. No. 3,870,415--Cornsweet, issued Mar. 11, 1975, and U.S. Pat. No. 4,007,990--McDevitt, Jr. et al. An example of such commercially available devices, is one marketed today and commercially available from Acuity Systems, Inc., of Reston, Va., known as an AUTO-LENSMETER. Such AUTO-LENSMETER combines a microcomputer and sophisticated laser technology to provide precise measurements of sphere, cylinder, axis and prism of a lens which are digitally displayed on a screen in standard prescription notation.
The basic concept embodied in such prior art devices is the utilization of a light beam source and a position-sensitve photoelectric detector surface which when the light beam is refracted by the lens under test, a corresponding deviation of the light beam from its normal path is detected by the light detector. The amount of deviation of a light beam which reflects the various refractive parameters of the lens under test is measured and an electrical output is produced which is electrically processed to provide an output indication representing one or more of the reflective properties of the optical system under test. Such deviation is detected by the use of a reflective surface, such as a mirror, which is mechanically adjusted to return the deviated light beam to its normal axis, the extent of such movement of the reflective surface or mirror providing, from the light detector, the electrical output signal which is processed for the display of the refractive parameters.
While such prior art devices provide extremely precise measurements, they fall short of the degree of automation and efficiency desired. This limitation is apparent through the necessity for manual manipulation of the adjustment mechanism to move the reflective surface back to its original position from the path of the deviated light beam; such as the thumbscrews in the aforementioned U.S. Pat. No. 4,007,990. Not only does the use of such manually operated adjustment mechanisms require specific skills not infrequently reducing the degree of accuracy available in such devices, but additional time is consumed in making the adjustment relegating such present-day devices to a semi-automatic and costly status.